ARM: dts: mt8173: support arm64 cpuidle-dt

This patch adds an idle-states node to describe the mt8173 idle states and
also adds references to the idle-states node in all CPU nodes.

Signed-off-by: Howard Chen <howard.chen@linaro.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8173.dtsi

@@ -51,27 +51,45 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-a53";
 			reg = <0x000>;
+			enable-method = "psci";
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu1: cpu@1 {
 			device_type = "cpu";
 			compatible = "arm,cortex-a53";
 			reg = <0x001>;
 			enable-method = "psci";
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu2: cpu@100 {
 			device_type = "cpu";
 			compatible = "arm,cortex-a57";
 			reg = <0x100>;
 			enable-method = "psci";
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu3: cpu@101 {
 			device_type = "cpu";
 			compatible = "arm,cortex-a57";
 			reg = <0x101>;
 			enable-method = "psci";
+			cpu-idle-states = <&CPU_SLEEP_0>;
+		};
+
+		idle-states {
+			entry-method = "arm,psci";
+
+			CPU_SLEEP_0: cpu-sleep-0 {
+				compatible = "arm,idle-state";
+				local-timer-stop;
+				entry-latency-us = <639>;
+				exit-latency-us = <680>;
+				min-residency-us = <1088>;
+				arm,psci-suspend-param = <0x0010000>;
+			};
 		};
 	};